I. Field
The present disclosure relates generally to communication, and more specifically to techniques for paging user equipments (UEs) in a wireless communication system.
II. Background
A UE in a wireless communication system (e.g., a cellular phone in a cellular system) may operate in one of several states, such as active and sleep states, at any given moment. In the active state, the UE may actively exchange data with one or more Node Bs (or base stations), e.g., for a voice or data call. In the sleep state, the UE may power down much of the time to conserve battery power and may wake up periodically to monitor for page messages sent to the UE. These page messages may alert the UE to the presence of an incoming call or may provide other information.
A wireless communication system expends radio resources to support paging. For example, the system may send paging indicators on a paging indicator channel (PICH) to indicate whether page messages are sent for UEs. The system may send page messages on a paging channel (PCH) to the UEs. A UE may quickly receive the paging indicators, determine whether a page message is sent to the UE, and either process the PCH if a page message is sent or go back to sleep immediately if no page messages are sent to the UE. The PICH and PCH are overhead channels that are used for all UEs. Hence, these overhead channels are typically sent at a sufficiently low rate and with sufficient transmit power such that even the most disadvantaged UE with the worst-case channel conditions can reliably receive the paging indicators and page messages. Furthermore, since the location of the UEs being paged may not be known, the system typically sends paging indicators and page messages from all cells in a wide area. Sending paging indicators and page messages on overhead channels over a wide area at low rate and/or high transmit power may consume much radio resources.
There is therefore a need in the art for techniques to efficiently page UEs.